Electric heater unit



July 16, 1940. B. H. R. SANDELL ELECTRIC HEATER UNIT Filed Sept; 9, 1958 INVENTOR 8v BHR. SADELL w T T A Patented July 16, 1940 UNiTED STATES ?A.TENT OFFICE eden Application September 9, 1938, Serial No. 229,191 In Sweden December 20, 1935 4 I Claims.

The present invention relates to electric heater units as used for electrically heated stoves and the like and comprising a number of substantially concentric heating portions which are intercon- 5 nected by means of substantially radial connection members so as to leave separating slots between the successive portions of the unit.

Heater units of this kind are already known in which the radial connection members are formed as permanently closed or tubular channels adapted to contain the connection wiring between the heating elements of the outer I concentric members of the unit and coupling means provided on a central socket. Such known construction has the drawback that it is difficult to mount the connection wiring in the closed channels and to provide them with the requisite insulation therein. Besides the casting of the unit is expensive due to the necessity of using core members for the said tubular channels.

. According to the present invention downwardly extending ribs are provided on the underside of the unit so as to. form thereon a number of substantially concentric channels adapted to contain the electric heating elements and one or more substantially radial channels adapted to contain the connection wiring between the heating elements in the outer portions of the unit and the coupling means of the central socket, said channels being open downwards and if desired adapted to be closed by a removable bottom plate.

Due to the downwardly open radial channels thus provided for on the underside of the heater unit the mounting and insulation of the electric connection wiring between the separate heating resistances and the central socket is greatly facilitated, and when the bottom plate has been fastened to the unit the resistors as well as the connection wiring are fully protected both against being touched and against being smeared by overflow of cooking liquids.

The subdivision of the heater unit in portions by means of arcuate slots surrounded by downwardly extending ribs which form intersecting concentric and radial channel-shaped spaces for the resistors and the connection wiring make it possible to use a removable one-piece bottomplate for all channels. This bottom plate may be manufactured from sheet metal by stamping, pressing or otherwise. The bottom plate may be fastened to the heater unit by means of screws which are screwed into studs positioned in the radial channels between the concentric channels where they do not occupy valuable space for the electric resistors and their insulation.

A preferred embodiment of the invention is illustrated in the accompanying drawing wherein:

Fig. l is a plan view of the heater unit;

Fig. 2 shows the heater unit from below, the bottom plate being partly broken away;

Fig. 3 is a section on the line IIIIII in Fig. l

Fig. 4 is a section on the line IV-IV in Fig. 1.

According to the embodiment shown the heater comprises a circular central portion I and two annular outer portions 2 and 3 which are concentric with respect to the central portion. The number of annular outer portions may naturally vary according to requirements.

The central portion and the outer portions are cast in one piece and separated by arcuate slots 8. In certain places 9 the slots 8 do not extend through the. plate but material is left between the successive portions of the unit so as to form radial connection members. Casting the unit is preferred to stamping the same from sheet metal because it is easier in the first case to make the heating surfaces of the difierent portions of the unit lie in exactly the same plane and remain so during the use, which of course is of great importance in a heater unit. Owing to the slots 8 the heater unit is also more expansible so that breakage due to heating stresses is avoided. Consequently, the dimensions of the material to be used may be reduced.

On its underside at the outer edge and around each of the arcuate slots 8 the heater unit is provided with downwardly extending ribs or flanges I8, and electric resistors [0 are embedded within a suitable insulation mass 20 and mounted in the concentric channel-shaped spaces confined by said ribs or flanges. A stamped out or cast bottom plate 5 is secured to the underside of the heater unit by means of screws 2| screwed into studs 22 provided on the underside of the unit in the radial channels.

In plan the bottom plate 5 has the same general shape as the heater, 1. e., it is provided with arcuate apertures 23 corresponding to the slots 8, and with radial connection portions 24 corresponding to the portions 9. The portions 24 of the bottom plate 5 extending into the spaces confined by the portions 9 and the downwardly extending ribs I8 thereon form radial channels 25 adapted to contain the connection wiring between the resistors I0 in the outer portions of the heater and contact pins I or the like mounted in a central insulating socket 6 carried by the heater.

If desired, the bottom plate 5 may be provided with upwardly extending ribs 26 at its outer edge and around each arcuate aperture 23, such ribs being adapted to be overlapped by the downwardly extending ribs [8 on the heater unit when the bottom plate is mounted thereon (compare Fig. 4) 1 Thus according to the invention the electric conductors are fully protected against overflow of cooking liquids and the like while at the same time being easily accessible after removal of the bottom plate 5.

The ribbed bottom plate 5 may be filled with a suitable insulation mass, as shown at 4 in Fig. 3.

Of course the invention is not limited to the bers so as to leave arcuate separating slots between the successive portions of the unit, a central socket carried by the unit and provided with electric coupling means, downwardly extending ribs on the underside of the heater unit around the outer edge thereof and surrounding each of the arcuate slots for forming a number of substantially concentric channels adapted to contain electric heating elements and one or more substantially radial channels interconnecting the concentric channels and adapted to contain connection Wiring between the heating elements in the outer portion or portions of the heater unit and the coupling means of the central socket, said channels being open downwards.

2. An electric heater unit according to claim 1 wherein the various channels formed by the downwardly extending ribs are closed by means of a removable bottom plate, said bottom plate being provided with apertures corresponding to the slots between the successive portions of the heater unit.

3. An electric heater unit comprising a circular central portion and one or more annular outer portions which are substantially concentric with the central portion and connected therewith by means of substantially radial connection members so as to leave arcuate slots between the successive portions of the unit, a central socket carried by the unit and provided with electric 'coupling means, downwardly extending ribs on the underside of the heater unit adapted to form thereon a number of substantially concentric channels adapted to contain electric heating elements and one or more substantially radial channels adapted to contain connection wiring between the heating elements in the outer portion or portions of the heater unit and the coupling means of the central socket, and a bottom plate provided with arcuate apertures corresponding to the arcuate slots between the portions of the heater unit and with upwardly extending ribs around its outer edge and around each arcuate aperture, said upwardly extending ribs being adapted to be overlapped by the downwardly extending ribs on the underside of the heater unit.

4. An electric heater unit according to claim 3 wherein the bottom plate is fastened to the heater unit by means of screws screwed into studs which are provided on the unit in the radial channels interconnecting the concentricchannels.

BROR HUGO RAGNVALD SANDELL. 

